Enter the diameter of the objective lens and the magnification into the calculator to determine the exit pupil. This calculator can also evaluate any of the variables given the others are known.

## Exit Pupil Formula

The following formula is used to calculate the exit pupil.

EP = D / M

Variables:

• EP is the exit pupil (mm) D is the diameter of the objective lens (mm) M is the magnification of the binoculars or telescope

To calculate the exit pupil, divide the diameter of the objective lens by the magnification of the binoculars or telescope. The result is the exit pupil in millimeters.

## What is an Exit Pupil?

The exit pupil is a term used in optics to describe the virtual aperture in an optical system. It is the point where the light rays coming from an object converge into the viewer’s eye through the optical system, such as a telescope or binoculars. The size of the exit pupil determines the amount of light that enters the eye, affecting the brightness of the image. It is typically measured in millimeters and can be calculated by dividing the diameter of the objective lens by the magnification of the system.

## How to Calculate Exit Pupil?

The following steps outline how to calculate the Exit Pupil.

1. First, determine the diameter of the objective lens (D) in millimeters.
2. Next, determine the magnification (M) of the binoculars or telescope.
3. Next, gather the formula from above = EP = D / M.
4. Finally, calculate the Exit Pupil.
5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem :

Use the following variables as an example problem to test your knowledge.

diameter of the objective lens (D) = 50 mm

magnification (M) = 10